Therapeutic applications of closed-loop brain stimulation. Success and expectations

The therapeutic application of brain stimulation is still limited to relatively few indications and small groups of patients due to variable efficacy. Individualization of stimulation parameters by employing a closed-loop system, i.e. synchronization of stimulation with endogenous brain activity with millisecond precision, has the potential to significantly improve the therapeutic efficacy when compared to open-loop systems. In this article the theoretical and experimental results are reviewed including first clinical trials that support the superiority of closed-loop brain stimulation, fundamental aspects in the development of closed loop methods are discussed and clinical studies which could quantify an increase in effectiveness are summarized. A significant increase in the indications for therapeutic applications of closed-loop systems is to be expected in the near future.